Sliding doors used in many homes and other small buildings are generally relatively heavy units comprised of a metal frame supporting a plate glass pane and movable within tracks supported between the floor and ceiling. For reasons such as convenience, heat conservation and safety, it is desireable to provide some power assist that will automatically close the door after it has been opened. Previous attempts to provide this feature are shown in U.S. Pat. Nos. 4,649,598, 4,003,102 and 3,334,444. All of these prior art devices utilize the general principle of a counterweiqht to provide a gravity assisted closing force. However, in each case they involved complicated mechanisms that were either overly expensive to manufacture and/or difficult to install and service.
Among the objects of the present invention are to provide an improved sliding door automatic closure device that can be installed to an existing door assembly without the need for special tools; that can be readily adjusted by an externally accessible control to optimize its operation; that is cosmetically compatible with the door on which it is installed; and that is particularly well adapted for ease and economy of manufacture.